As shown in FIG. 1, in conventional type vertically aligned mode liquid crystal displays, a mode is adopted in which bumps 5 for controlling a motion direction of liquid crystal molecules 14 are formed on a transparent common electrode 4 of a color filter side substrate 1, and slits 9 for controlling a motion direction of the liquid crystal molecules 14 are provided in transparent pixel electrodes 8 of an active matrix substrate 13, the bumps 5 and the slits 9 determine the motion direction of the liquid crystal molecules 14 serving as one set. There is also provided a method in which slits for controlling the motion direction of the liquid crystal molecules 14 in place of bumps 5 are formed on a transparent common electrode 4 on the color filter side substrate 1. Both of these modes are put in practical use for mass-production.
In the conventional type multi-domain vertically aligned mode liquid crystal displays, it is necessary that such bumps or slits are formed on the transparent common electrode in the color filter side substrate, which requires one excessive photo mask process. Therefore, in this conventional technology, cost increase is unavoidable.
Moreover, in the vertically aligned mode liquid crystal displays with the bumps 5 formed in the color filter layer 3 side, as shown in FIG. 1, when a width, a pitch, and an angle of the slope of the bumps 5 are not precisely controlled, variation in the tilting degree of liquid crystal molecules 14 is occurred, which frequently causes unevenness in half tone areas.
Since the bumps are made of positive type photoresists, perfect removal of organic solvents, and furthermore hardening by baking at high temperatures of no less than 200 degrees are furthermore required, leading to difficulty in shortening the processes. When contaminants are eluted out into liquid crystals from the bumps of positive type photoresists, a phenomenon of afterimage will occur, resulting in reliability problems.
In color filter substrates using the conventional bumps, positive type photoresists are used as materials for the bumps, and therefore, when a defect occurs in the application process of a vertical alignment film 6 and reworking is required, a dry ashing method using oxygen plasma can not be used. Therefore, a wet remove method requiring high running cost using organic solvents has to be used, which causes a disadvantage requiring a very high reworking cost.
In vertically aligned mode liquid crystal displays using the conventional type bumps and slits, when a display switchovers to a half tone display from a black display, or to a half tone display from a white display, there arises defects that the liquid crystals operate in a slow response speed.